This invention relates generally to information storage and retrieval, and more particularly to high-density optical archival memories.
My copending applications Ser. No. 430,933 entitled HIGH DENSITY OPTICAL MEMORY STORAGE MEANS EMPLOYING A MULTIPLE LENS ARRAY, now U.S. Pat. No. 3,898,005; and Ser. No. 430,932 entitled MEANS EMPLOYING A MULTIPLE LENS ARRAY FOR READING FROM A HIGH DENSITY OPTICAL MEMORY STORAGE, now U.S. Pat. No. 3,899,778, disclose optical storage systems employing relatively low-energy light sources with high resolution photosensitive storage media.
Techniques for modifying a storage medium with a laser beam are well known in the art. The major advantages of this process for archival or write/read-only storage are low cost of the storage medium, virtually simultaneous access to the recorded data because no latent-image processing of the medium is required, and the reduced requirement for controlling environmental conditions which may affect the storage medium. Prior art archival stores utilizing laser recording employed recording lenses having a relatively low ratio of the focal length to aperture size, e.g. 0.33, for compatibility with the desired optical reduction and resolution of the recorded data. Such recording lenses limit the physical size of the recording field. Prior art systems characteristically employ physical movement of apparatus relatively close to the recording plane, viz., either movement of the medium itself in order to provide additional storage fields, or as in the aforementioned copending application Ser. No. 430,933, movement of an apertured plate in order to mask all but a selected one of plurality of recording lenses. Such physical movement of apparatus near the recording plane does not lend itself to random access systems.